Conventional construction methods generally adopt wooden corners as the main construction material for the construction of groundwork, because wooden corners can be nailed by a hammer. As a result, it may cause a relatively high error in precision and also create problems to the construction when adjusting the precision. Furthermore, it is necessary to saw the wooden corners one by one, not only wasting working time, but also making the construction inefficient. Since the wooden corner is large and heavy, therefore it takes more time for its transportation, and thus increasing the cost accordingly. Furthermore, wooden corners are easily bitten by termites and moistened, which will cause deformations and damages to the floor.